Eight speed automatic transmission

ABSTRACT

An automatic transmission includes an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may be either clutches or brakes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/909,778 filed on Apr. 3, 2007. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed automatictransmission having a plurality of planetary gear sets and a pluralityof torque transmitting devices and more particularly to an eight speedautomatic transmission having four planetary gear sets and a pluralityof torque transmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed automatic transmission uses a combination offriction clutches, planetary gear arrangements and fixedinterconnections to achieve a plurality of gear ratios. The number andphysical arrangement of the planetary gear sets, generally, are dictatedby packaging, cost and desired speed ratios.

While current automatic transmissions achieve their intended purpose,the need for new and improved transmission configurations which exhibitimproved performance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed automatictransmission.

SUMMARY

An automatic transmission is provided that includes an input member, anoutput member, four planetary gear sets, a plurality of coupling membersand a plurality of torque transmitting devices. Each of the planetarygear sets includes first, second and third members. The torquetransmitting devices may be either clutches or brakes.

One embodiment of the transmission includes an input member, an outputmember, and first, second, third and fourth planetary gear sets eachhaving first, second and third members. A first interconnecting membercontinuously interconnects the first member of the first planetary gearset with the first member of the second planetary gear set and thesecond member of the third planetary gear set. A second interconnectingmember continuously interconnects the second member of the firstplanetary gear set with the third member of the second planetary gearset. A third interconnecting member continuously interconnects thesecond member of the second planetary gear set with the third member ofthe fourth planetary gear set. Five torque transmitting devices areselectively engageable to interconnect one of the first members, secondmembers, and third members with at least one of the first members,second members, third members, and a stationary member. The torquetransmitting devices are selectively engageable in combinations of atleast three to establish at least eight forward speed ratios and atleast one reverse speed ratio between the input member and the outputmember.

In one aspect of the present invention, a first of the five torquetransmitting devices is selectively engageable to interconnect at leastone of the second member of the fourth planetary gear set and the inputmember with at least one of the first member of the second planetarygear set, the first member of the first planetary gear set, and thesecond member of the third planetary gear set.

In another aspect of the present invention, a second of the five torquetransmitting devices is selectively engageable to interconnect at leastone of the third member of the second planetary gear set and the secondmember of the first planetary gear set with at least one of the thirdmember of the third planetary gear set and the output member.

In yet another aspect of the present invention, a third of the fivetorque transmitting devices is selectively engageable to interconnectthe first member of the fourth planetary gear set with the first memberof the third planetary gear set.

In yet another aspect of the present invention, a fourth of the fivetorque transmitting devices is selectively engageable to interconnectthe third member of the first planetary gear with the stationary member.

In yet another aspect of the present invention, a fifth of the fivetorque transmitting devices is selectively engageable to interconnectthe first member of the fourth planetary gear set with the stationarymember.

In yet another aspect of the present invention, a second of the fivetorque transmitting devices is selectively engageable to interconnectthe first member of the fourth planetary gear set with the first memberof the third planetary gear set.

In yet another aspect of the present invention, a third of the fivetorque transmitting devices is selectively engageable to interconnect atleast one of the third member of the second planetary gear set and thesecond member of the first planetary gear set with the first member ofthe third planetary gear set.

In yet another aspect of the present invention, the first members aresun gears, the second members are carrier members, and the third membersare ring gears.

In yet another aspect of the present invention, the first member of thefirst planetary gear set is a carrier member, the second member of thefirst planetary gear set is a ring gear, the third member of the firstplanetary gear set is a sun gear, the first member of the secondplanetary gear set is a ring gear, the second member of the secondplanetary gear set is a sun gear, the third member of the secondplanetary gear set is a carrier member, the first member of the thirdplanetary gear set is a ring gear, the second member of the thirdplanetary gear set is a sun gear, the third member of the thirdplanetary gear set is a carrier member, the first member of the fourthplanetary gear set is a ring gear, the second member of the fourthplanetary gear set is a carrier member, and the third member of thefourth planetary gear set is a sun gear.

In yet another aspect of the present invention, the input member iscontinuously interconnected with the second member of the fourthplanetary gear set and the output member is continuously interconnectedwith the third member of the third planetary gear set.

Another embodiment of the transmission of the present invention includesan input member, an output member, first, second, third and fourthplanetary gear sets each having a sun gear, a carrier member, and a ringgear, wherein the input member is continuously interconnected with thecarrier member of the fourth planetary gear set and the output member iscontinuously interconnected with the ring gear of the third planetarygear set. A first interconnecting member continuously interconnects thesun gear of the first planetary gear set with the sun gear of the secondplanetary gear set and the carrier member of the third planetary gearset. A second interconnecting member continuously interconnects thecarrier member of the first planetary gear set with the ring gear of thesecond planetary gear set. A third interconnecting member continuouslyinterconnects the carrier member of the second planetary gear set withthe ring gear of the fourth planetary gear set. A first torquetransmitting device is selectively engageable to interconnect at leastone of the carrier member of the fourth planetary gear set and the inputmember with at least one of the sun gear of the second planetary gearset, the sun gear of the first planetary gear set, and the carriermember of the third planetary gear set. A second torque transmittingdevice is selectively engageable to interconnect at least one of thering gear of the second planetary gear set and the carrier member of thefirst planetary gear set with at least one of the ring gear of the thirdplanetary gear set and the output member. A third torque transmittingdevice is selectively engageable to interconnect the sun gear of thefourth planetary gear set with the sun gear of the third planetary gearset. A fourth torque transmitting device is selectively engageable tointerconnect the ring gear of the first planetary gear with a stationarymember. A fifth torque transmitting device is selectively engageable tointerconnect the sun gear of the fourth planetary gear set with thestationary member. The torque transmitting devices are selectivelyengageable in combinations of at least three to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.

Yet another embodiment of the transmission of the present inventionincludes an input member, an output member, first, second, third andfourth planetary gear sets each having a sun gear, a carrier member, anda ring gear, wherein the input member is continuously interconnectedwith the carrier member of the fourth planetary gear set and the outputmember is continuously interconnected with the carrier member of thethird planetary gear set. A first interconnecting member continuouslyinterconnects the carrier member of the first planetary gear set withthe ring gear of the second planetary gear set and the sun gear of thethird planetary gear set. A second interconnecting member continuouslyinterconnects the ring gear of the first planetary gear set with thecarrier member of the second planetary gear set. A third interconnectingmember continuously interconnects the sun gear of the second planetarygear set with the sun gear of the fourth planetary gear set. A firsttorque transmitting device is selectively engageable to interconnect atleast one of the carrier member of the fourth planetary gear set and theinput member with at least one of the ring gear of the second planetarygear set, the carrier member of the first planetary gear set, and thesun gear of the third planetary gear set. A second torque transmittingdevice is selectively engageable to interconnect the ring gear of thefourth planetary gear set with the ring gear of the third planetary gearset. A third torque transmitting device is selectively engageable tointerconnect at least one of the carrier member of the second planetarygear set and the ring gear of the first planetary gear set with the ringgear of the third planetary gear set. A fourth torque transmittingdevice is selectively engageable to interconnect the sun gear of thefirst planetary gear with a stationary member. A fifth torquetransmitting device is selectively engageable to interconnect the ringgear of the fourth planetary gear set with the stationary member. Thetorque transmitting devices are selectively engageable in combinationsof at least three to establish at least eight forward speed ratios andat least one reverse speed ratio between the input member and the outputmember.

Further aspects and advantages of the present invention will becomeapparent by reference to the following description and appended drawingswherein like reference numbers refer to the same component, element orfeature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speed automatictransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of the eight speedautomatic transmission according to the present invention;

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting devices in each of the available forward andreverse speeds or gear ratios of the automatic transmission illustratedin FIGS. 1 and 2;

FIG. 4 is a lever diagram of another embodiment of an eight speedautomatic transmission according to the present invention;

FIG. 5 is a diagrammatic view of another embodiment of the eight speedautomatic transmission according to the present invention; and

FIG. 6 is a truth table presenting the state of engagement of thevarious torque transmitting devices in each of the available forward andreverse speeds or gear ratios of the automatic transmission illustratedin FIGS. 4 and 5.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe elements of the four planetary gear sets. These permanent mechanicalconnections relate the transmission embodiments. More specifically, afirst component or element of a first planetary gear set is permanentlycoupled to a first component or element of a second planetary gear set.A second component or element of the first planetary gear set ispermanently coupled to a second component or element of the secondplanetary gear set and to a second component or element of a thirdplanetary gear set. A third component or element of the second planetarygear set is permanently coupled to a third component or element of afourth planetary gear set.

Referring now to FIG. 1, a first embodiment of an eight speed automatictransmission 10 is illustrated in a lever diagram format. A leverdiagram is a schematic representation of the components of a mechanicaldevice such as an automatic transmission. Each individual leverrepresents a planetary gear set wherein the three basic mechanicalcomponents of the planetary gear are each represented by a node.Therefore, a single lever contains three nodes: one for the sun gearmember, one for the planet gear carrier, and one for the ring gearmember. The relative length between the nodes of each lever can be usedto represent the ring-to-sun ratio of each respective gearset. Theselever ratios, in turn, are used to vary the gear ratios of thetransmission in order to achieve an appropriate ratios and ratioprogression. Mechanical couplings or interconnections between the nodesof the various planetary gear sets are illustrated by thin, horizontallines and torque transmitting devices such as clutches and brakes arepresented as interleaved fingers. If the device is a brake, one set ofthe fingers is grounded. Further explanation of the format, purpose anduse of lever diagrams can be found in SAE Paper 810102, which is herebyfully incorporated by reference.

The automatic transmission 10 includes an input shaft 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C, and an output shaft 22. The first node 14A of the first planetarygear set 14 is coupled to the first node 16A of the second planetarygear set 16. The second node 14B of the first planetary gear set 14 iscoupled to the second node 16B of the second planetary gear set 16. Thesecond node 14B of the first planetary gear set 14 is coupled to thesecond node 18B of the third planetary gear set 18. The third node 16Cof the second planetary gear set 16 is coupled to the third node 20C ofthe fourth planetary gear set 20.

The input shaft 12 is coupled to the first node 20A of the fourthplanetary gear set 20. The output shaft 22 is coupled to the first node18A of the third planetary gear set 18. A first clutch 26 selectivelyconnects the first node 20A of the fourth planetary gear set 20 to thesecond node 16B of the second planetary gear set 16. A second clutch 28selectively connects the first node 14A of the first planetary gear set14 to the first node 18A of the third planetary gear set 18. A thirdclutch 30 selectively connects the second node 20B of the fourthplanetary gear set 20 to the third node 18C of the third planetary gearset 18. A first brake 32 selectively connects the third node 14C of thefirst planetary gear set 14 to a ground, stationary member, ortransmission housing 40. Finally, a second brake 34 selectively connectsthe second node 20B of the fourth planetary gear set 20 to a ground,stationary member, or transmission housing 40.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofan embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brakes and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gearmembers, ring gear members, planet gears and planet gear carriermembers.

For example, the first planetary gear set 14 includes a first sun gearmember 14B, a first ring gear member 14C, and a first planet carriermember 14A that includes a plurality of planet gears 14D rotatablydisposed thereon. The planet gears 14D are each intermeshed with boththe first sun gear member 14B and the first ring gear member 14C. Thesecond planetary gear set 16 includes a second sun gear member 16B, asecond ring gear member 16A, and a second planet carrier member 16C thatincludes a plurality of planet gears 16D rotatably disposed thereon. Theplanet gears 16D are each intermeshed with both the second sun gearmember 16B and the second ring gear member 16A. The third planetary gearset 18 includes a third sun gear member 18C, a third ring gear member18A, and a third planet carrier member 18B that includes a plurality ofplanet gears 18D rotatably disposed thereon. The planet gears 18D areeach intermeshed with both the third sun gear member 18C and the thirdring gear member 18A. The fourth planetary gear set 20 includes a fourthsun gear member 20B, a fourth ring gear member 20C, and a fourth planetcarrier member 20A that includes a first plurality of planet gears 20Dand a second plurality of planet gears 20E rotatably disposed thereon.The planet gears 20D are each intermeshed with both the planet gears 20Eand the fourth ring gear member 20C. The planet gears 20E are eachintermeshed with both the planet gears 20D and the fourth sun gearmember 20B.

The input shaft 12 is coupled to and directly drives the fourthplanetary carrier member 20A. A first shaft or interconnecting member 42couples the fourth ring gear member 20C to the second planet carriermember 16C. A second shaft or interconnecting member 44 couples thefirst clutch 26 to the second sun gear member 16B. A third shaft orinterconnecting member 46 couples the fourth sun gear member 20B to thethird clutch 30. A fourth shaft or interconnecting member 48 couples thesecond ring gear member 16A to the first planet carrier member 14A. Afifth shaft or interconnecting member 50 couples the second sun gearmember 16B to the first sun gear member 14B. A sixth shaft orinterconnecting member 52 couples the third clutch 30 to the third sungear member 18C. A seventh shaft or interconnecting member 54 couplesthe second clutch 28 to the third ring gear member 18A. An eighth shaftor interconnecting member 56 couples the first sun gear member 14B tothe third planet carrier member 18B. A ninth shaft or interconnectingmember 58 couples the fourth planet carrier member 20A to the firstclutch 26. A tenth shaft or interconnecting member 60 couples the firstplanet carrier member 14A to the second clutch 28.

The first clutch 26 selectively couples the fourth planet carrier member20A to the second sun gear member 16B and the first sun gear member 14B.The second clutch 28 selectively couples the first planet carrier member14A to the third ring gear member 18A. The third clutch 30 selectivelycouples the fourth sun gear member 20B to the third sun gear member 18C.The first brake 32 selectively couples the first ring gear member 14C toa ground, stationary member, or transmission housing 40. The secondbrake 34 selectively couples the fourth sun gear member 20B to a ground,stationary member, or transmission housing 40. The output shaft 22 iscoupled to and driven by the third ring gear member 18A.

Referring now to FIGS. 2 and 3, the operation of the eight speedautomatic transmission 10 will be described. It will be appreciated thatthe automatic transmission 10 is capable of transmitting torque from theinput shaft 12 to the output shaft 22 in eight forward speed or torqueratios and one reverse speed or torque ratio. Each forward and reversespeed or torque ratio is attained by engagement of one or more of theclutches or brakes as will be explained below. FIG. 3 is a truth tablepresenting the various combinations of clutches and brakes that areactivated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of theautomatic transmission 10.

To establish gear ratios, three torque transmitting devices are engagedfor each gear state. The engaged clutches are represented by an “X” ineach respective row. For example, to establish reverse gear, the firstbrake 32, the second clutch 28, and the third clutch 30 are engaged oractivated. The first brake 32 couples the first ring gear member 14C toground. The second clutch 28 couples the first planet carrier member 14Ato the third ring gear member 18A. The third clutch 30 couples thefourth sun gear member 20B to the third sun gear member 18C. Likewise,the eight forward ratios are achieved through different combinations ofclutch engagement as per FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed automatic transmission 10 assumes, firstof all, that all clutches and brakes not specifically referenced in agiven gear state are inactive or disengaged and, second of all, thatduring gear member shifts, i.e., changes of gear state, between at leastadjacent gear states, a clutch or brake engaged or activated in bothgear states will remain engaged or activated.

Turning now to FIG. 4, a lever diagram for another embodiment of aneight speed automatic transmission 100 is illustrated. The automatictransmission 100 includes an input shaft 112, a first planetary gear set114 having three nodes: a first node 114A, a second node 114B and athird node 114C, a second planetary gear set 116 having three nodes: afirst node 116A, a second node 116B and a third node 116C, a thirdplanetary gear set 118 having three nodes: a first node 118A, a secondnode 118B and a third node 118C, a fourth planetary gear set 120 havingthree nodes: a first node 120A, a second node 120B and a third node120C, and an output shaft 122.

The input shaft 112 is coupled to the first node 120A of the fourthplanetary gear set 120. The output shaft 122 is coupled to the firstnode 118A of the third planetary gear set 118. The first node 114A ofthe first planetary gear set 114 is coupled to the first node 116A ofthe second planetary gear set 116. The second node 114B of the firstplanetary gear set 114 is coupled to the second node 116B of the secondplanetary gear set 116. The second node 114B of the first planetary gearset 114 is coupled to the second node 118B of the third planetary gearset 118. The third node 116C of the second planetary gear set 116 iscoupled to the third node 120C of the fourth planetary gear set 120.

A first clutch 126 selectively connects the first node 120A of thefourth planetary gear set 120 to the second node 116B of the secondplanetary gear set 116. A second clutch 128 selectively connects thesecond node 120B of the fourth planetary gear set 120 to the third node118C of the third planetary gear set 118. A third clutch 130 selectivelyconnects the first node 114A of the first planetary gear set 114 to thethird node 118C of the third planetary gear set 118. A first brake 132selectively connects the second node 120B of the fourth planetary gearset 120 to a ground, stationary member, or transmission housing 140.Finally, a second brake 134 selectively connects the third node 114C ofthe first planetary gear set 114 to a ground, stationary member, ortransmission housing 140.

Referring now to FIG. 5, a stick diagram presents a schematic layout ofthe second embodiment of the eight speed transmission 100 according tothe present invention. In FIG. 5, the numbering from the lever diagramof FIG. 4 is carried over. The clutches, brakes and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gearmembers, ring gear members, planet gears and planet gear carriermembers.

For example, the first planetary gear set 114 includes a first sun gearmember 114C, a first ring gear member 114A, and a first planet carriermember 114B that includes a plurality of planet gears 114D rotatablydisposed thereon. The planet gears 114D are each intermeshed with boththe first sun gear member 114C and the first ring gear member 114A. Thesecond planetary gear set 116 includes a second sun gear member 116C, asecond ring gear member 116B, and a second planet carrier member 116Athat includes a plurality of planet gears 116D rotatably disposedthereon. The planet gears 116D are each intermeshed with both the secondsun gear member 116C and the second ring gear member 116B. The thirdplanetary gear set 118 includes a third sun gear member 118B, a thirdring gear member 118C, and a third planet carrier member 118A thatincludes a plurality of planet gears 118D rotatably disposed thereon.The planet gears 118D are each intermeshed with both the third sun gearmember 118B and the third ring gear member 118C. The fourth planetarygear set 120 includes a fourth sun gear member 120C, a fourth ring gearmember 120B, and a fourth planet carrier member 120A that includes aplurality of planet gears 120D rotatably disposed thereon. The planetgears 120D are each intermeshed with both the fourth sun gear member120C and the fourth ring gear member 120B.

The input shaft 112 is coupled to and directly drives the fourthplanetary carrier member 120A and the first clutch 126. A first shaft orinterconnecting member 142 couples the fourth sun gear member 120C tothe second sun gear member 116C. A second shaft or interconnectingmember 144 couples the fourth ring gear member 120B to the second clutch128. A third shaft or interconnecting member 146 couples the secondplanet carrier member 116A to the first ring gear member 114A. A fourthshaft or interconnecting member 148 couples the second ring gear member116B to the first planet carrier member 114B. A fifth shaft orinterconnecting member 150 couples the first ring gear member 114A tothe third clutch 130. A sixth shaft or interconnecting member 152couples the first planet carrier member 114B to the third sun gearmember 118B. A seventh shaft or interconnecting member 154 couples thesecond clutch 128 to the third ring gear member 118C. An eighth shaft orinterconnecting member 156 couples the third clutch 130 to the thirdring gear member 118C.

The first clutch 126 selectively couples the fourth planet carriermember 120A and the input shaft 112 to the second ring gear member 116Band the first planet carrier member 114B. The second clutch 128selectively couples the fourth ring gear member 120B to the third ringgear member 118C. The third clutch 130 selectively couples the firstring gear member 114A to the third ring gear member 118C. The firstbrake 132 selectively couples the fourth ring gear member 120B to aground, stationary member, or transmission housing 140. The second brake134 selectively couples the first sun gear member 114C to a ground,stationary member, or transmission housing 140. The output shaft 122 iscoupled to and driven by the third planet carrier member 118A.

Referring now to FIGS. 5 and 6, the operation of the eight speedautomatic transmission 100 will be described. It will be appreciatedthat the automatic transmission 100 is capable of transmitting torquefrom the input shaft 112 to the output shaft 122 in eight forward speedor torque ratios and one reverse speed or torque ratio. Each forward andreverse speed or torque ratio is attained by engagement of one or moreof the clutches or brakes as will be explained below. FIG. 6 is a truthtable presenting the various combinations of clutches and brakes thatare activated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of theautomatic transmission 100.

To establish gear ratios, three torque transmitting devices are engagedfor each gear state. The engaged elements are represented by an “X” ineach respective row. For example, to establish reverse gear, the firstbrake 132, the second clutch 128, and the third clutch 130 are engagedor activated. The first brake 132 couples the fourth ring gear member120B to ground. The second clutch 128 couples the fourth ring gearmember 120B to the third ring gear member 118C. The third clutch 130couples the first ring gear member 114A to the third ring gear member118C. Likewise, the eight forward ratios are achieved through differentcombinations of clutch engagement as shown in FIG. 6.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed automatic transmission 100 assumes, firstof all, that all clutches and brakes not specifically referenced in agiven gear state are inactive or disengaged and, second of all, thatduring gear member shifts, i.e., changes of gear state, between at leastadjacent gear states, a clutch or brake engaged or activated in bothgear states will remain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a first interconnecting member continuouslyinterconnecting the first member of the first planetary gear set withthe first member of the second planetary gear set and the second memberof the third planetary gear set; a second interconnecting membercontinuously interconnecting the second member of the first planetarygear set with the third member of the second planetary gear set; a thirdinterconnecting member continuously interconnecting the second member ofthe second planetary gear set with the third member of the fourthplanetary gear set; and five torque transmitting devices selectivelyengageable to interconnect one of the first members, second members, andthird members with at least one of the first members, second members,third members, and a stationary member; and wherein the torquetransmitting devices are selectively engageable in combinations of atleast three to establish at least eight forward speed ratios and atleast one reverse speed ratio between the input member and the outputmember.
 2. The transmission of claim 1 wherein a first of the fivetorque transmitting devices is selectively engageable to interconnect atleast one of the second member of the fourth planetary gear set and theinput member with at least one of the first member of the secondplanetary gear set, the first member of the first planetary gear set,and the second member of the third planetary gear set.
 3. Thetransmission of claim 2 wherein a second of the five torque transmittingdevices is selectively engageable to interconnect at least one of thethird member of the second planetary gear set and the second member ofthe first planetary gear set with at least one of the third member ofthe third planetary gear set and the output member.
 4. The transmissionof claim 3 wherein a third of the five torque transmitting devices isselectively engageable to interconnect the first member of the fourthplanetary gear set with the first member of the third planetary gearset.
 5. The transmission of claim 4 wherein a fourth of the five torquetransmitting devices is selectively engageable to interconnect the thirdmember of the first planetary gear with the stationary member.
 6. Thetransmission of claim 5 wherein a fifth of the five torque transmittingdevices is selectively engageable to interconnect the first member ofthe fourth planetary gear set with the stationary member.
 7. Thetransmission of claim 2 wherein a second of the five torque transmittingdevices is selectively engageable to interconnect the first member ofthe fourth planetary gear set with the first member of the thirdplanetary gear set.
 8. The transmission of claim 7 wherein a third ofthe five torque transmitting devices is selectively engageable tointerconnect at least one of the third member of the second planetarygear set and the second member of the first planetary gear set with thefirst member of the third planetary gear set.
 9. The transmission ofclaim 8 wherein a fourth of the five torque transmitting devices isselectively engageable to interconnect the third member of the firstplanetary gear with the stationary member.
 10. The transmission of claim9 wherein a fifth of the five torque transmitting devices is selectivelyengageable to interconnect the first member of the fourth planetary gearset with the stationary member.
 11. The transmission of claim 1 whereinthe first members are sun gears, the second members are carrier members,and the third members are ring gears.
 12. The transmission of claim 1wherein the first member of the first planetary gear set is a carriermember, the second member of the first planetary gear set is a ringgear, the third member of the first planetary gear set is a sun gear,the first member of the second planetary gear set is a ring gear, thesecond member of the second planetary gear set is a sun gear, the thirdmember of the second planetary gear set is a carrier member, the firstmember of the third planetary gear set is a ring gear, the second memberof the third planetary gear set is a sun gear, the third member of thethird planetary gear set is a carrier member, the first member of thefourth planetary gear set is a ring gear, the second member of thefourth planetary gear set is a carrier member, and the third member ofthe fourth planetary gear set is a sun gear.
 13. The transmission ofclaim 1 wherein the input member is continuously interconnected with thesecond member of the fourth planetary gear set and the output member iscontinuously interconnected with the third member of the third planetarygear set.
 14. The transmission of claim 1 wherein the stationary memberis a transmission housing.
 15. A transmission comprising: an inputmember; an output member; first, second, third and fourth planetary gearsets each having first, second and third members, wherein the inputmember is continuously interconnected with the second member of thefourth planetary gear set and the output member is continuouslyinterconnected with the third member of the third planetary gear set; afirst interconnecting member continuously interconnecting the firstmember of the first planetary gear set with the first member of thesecond planetary gear set and the second member of the third planetarygear set; a second interconnecting member continuously interconnectingthe second member of the first planetary gear set with the third memberof the second planetary gear set; a third interconnecting membercontinuously interconnecting the second member of the second planetarygear set with the third member of the fourth planetary gear set; a firsttorque transmitting device selectively engageable to interconnect atleast one of the second member of the fourth planetary gear set and theinput member with at least one of the first member of the secondplanetary gear set, the first member of the first planetary gear set,and the second member of the third planetary gear set; a second torquetransmitting device selectively engageable to interconnect at least oneof the third member of the second planetary gear set and the secondmember of the first planetary gear set with at least one of the thirdmember of the third planetary gear set and the output member; a thirdtorque transmitting device selectively engageable to interconnect thefirst member of the fourth planetary gear set with the first member ofthe third planetary gear set; a fourth torque transmitting deviceselectively engageable to interconnect the third member of the firstplanetary gear with a stationary member; and a fifth torque transmittingdevice selectively engageable to interconnect the first member of thefourth planetary gear set with the stationary member, and wherein thetorque transmitting devices are selectively engageable in combinationsof at least three to establish at least eight forward speed ratios andat least one reverse speed ratio between the input member and the outputmember.
 16. The transmission of claim 15 wherein the first members aresun gears, the second members are carrier members, and the third membersare ring gears.
 17. A transmission comprising: an input member; anoutput member; first, second, third and fourth planetary gear sets eachhaving first, second and third members, wherein the input member iscontinuously interconnected with the second member of the fourthplanetary gear set and the output member is continuously interconnectedwith the third member of the third planetary gear set; a firstinterconnecting member continuously interconnecting the first member ofthe first planetary gear set with the first member of the secondplanetary gear set and the second member of the third planetary gearset; a second interconnecting member continuously interconnecting thesecond member of the first planetary gear set with the third member ofthe second planetary gear set; a third interconnecting membercontinuously interconnecting the second member of the second planetarygear set with the third member of the fourth planetary gear set; a firsttorque transmitting device selectively engageable to interconnect atleast one of the second member of the fourth planetary gear set and theinput member with at least one of the first member of the secondplanetary gear set, the first member of the first planetary gear set,and the second member of the third planetary gear set; a second torquetransmitting device selectively engageable to interconnect the firstmember of the fourth planetary gear set with the first member of thethird planetary gear set; a third torque transmitting device selectivelyengageable to interconnect at least one of the third member of thesecond planetary gear set and the second member of the first planetarygear set with the first member of the third planetary gear set; a fourthtorque transmitting device selectively engageable to interconnect thethird member of the first planetary gear with a stationary member; and afifth torque transmitting device selectively engageable to interconnectthe first member of the fourth planetary gear set with the stationarymember, and wherein the torque transmitting devices are selectivelyengageable in combinations of at least three to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.
 18. The transmission of claim 17wherein the first member of the first planetary gear set is a carriermember, the second member of the first planetary gear set is a ringgear, the third member of the first planetary gear set is a sun gear,the first member of the second planetary gear set is a ring gear, thesecond member of the second planetary gear set is a sun gear, the thirdmember of the second planetary gear set is a carrier member, the firstmember of the third planetary gear set is a ring gear, the second memberof the third planetary gear set is a sun gear, the third member of thethird planetary gear set is a carrier member, the first member of thefourth planetary gear set is a ring gear, the second member of thefourth planetary gear set is a carrier member, and the third member ofthe fourth planetary gear set is a sun gear.
 19. A transmissioncomprising: an input member; an output member; first, second, third andfourth planetary gear sets each having a sun gear, a carrier member, anda ring gear, wherein the input member is continuously interconnectedwith the carrier member of the fourth planetary gear set and the outputmember is continuously interconnected with the ring gear of the thirdplanetary gear set; a first interconnecting member continuouslyinterconnecting the sun gear of the first planetary gear set with thesun gear of the second planetary gear set and the carrier member of thethird planetary gear set; a second interconnecting member continuouslyinterconnecting the carrier member of the first planetary gear set withthe ring gear of the second planetary gear set; a third interconnectingmember continuously interconnecting the carrier member of the secondplanetary gear set with the ring gear of the fourth planetary gear set;a first torque transmitting device selectively engageable tointerconnect at least one of the carrier member of the fourth planetarygear set and the input member with at least one of the sun gear of thesecond planetary gear set, the sun gear of the first planetary gear set,and the carrier member of the third planetary gear set; a second torquetransmitting device selectively engageable to interconnect at least oneof the ring gear of the second planetary gear set and the carrier memberof the first planetary gear set with at least one of the ring gear ofthe third planetary gear set and the output member; a third torquetransmitting device selectively engageable to interconnect the sun gearof the fourth planetary gear set with the sun gear of the thirdplanetary gear set; a fourth torque transmitting device selectivelyengageable to interconnect the ring gear of the first planetary gearwith a stationary member; and a fifth torque transmitting deviceselectively engageable to interconnect the sun gear of the fourthplanetary gear set with the stationary member, and wherein the torquetransmitting devices are selectively engageable in combinations of atleast three to establish at least eight forward speed ratios and atleast one reverse speed ratio between the input member and the outputmember.
 20. A transmission comprising: an input member; an outputmember; first, second, third and fourth planetary gear sets each havinga sun gear, a carrier member, and a ring gear, wherein the input memberis continuously interconnected with the carrier member of the fourthplanetary gear set and the output member is continuously interconnectedwith the carrier member of the third planetary gear set; a firstinterconnecting member continuously interconnecting the carrier memberof the first planetary gear set with the ring gear of the secondplanetary gear set and the sun gear of the third planetary gear set; asecond interconnecting member continuously interconnecting the ring gearof the first planetary gear set with the carrier member of the secondplanetary gear set; a third interconnecting member continuouslyinterconnecting the sun gear of the second planetary gear set with thesun gear of the fourth planetary gear set; a first torque transmittingdevice selectively engageable to interconnect at least one of thecarrier member of the fourth planetary gear set and the input memberwith at least one of the ring gear of the second planetary gear set, thecarrier member of the first planetary gear set, and the sun gear of thethird planetary gear set; a second torque transmitting deviceselectively engageable to interconnect the ring gear of the fourthplanetary gear set with the ring gear of the third planetary gear set; athird torque transmitting device selectively engageable to interconnectat least one of the carrier member of the second planetary gear set andthe ring gear of the first planetary gear set with the ring gear of thethird planetary gear set; a fourth torque transmitting deviceselectively engageable to interconnect the sun gear of the firstplanetary gear with a stationary member; and a fifth torque transmittingdevice selectively engageable to interconnect the ring gear of thefourth planetary gear set with the stationary member, and wherein thetorque transmitting devices are selectively engageable in combinationsof at least three to establish at least eight forward speed ratios andat least one reverse speed ratio between the input member and the outputmember.